Simulating Furrow-Dike Impacts on Runoff and Sorghum Yields

ABSTRACT PREDICTIONS of water-table positions and drain spacings computed using theoretical transient drain spacing equations were compared with the measured performance of subsurface drains installed in a relatively shallow lacustrine soil in southern Alberta, Canada. Results from empirical drain spacing equations, which were developed by measuring the performance of subsurface drains installed at depths of 0.76, 1.22 and 1.68 m, were compared with computations using theoretical drainage equations. The Bouwer and van Schilfgaarde equation, using a C-factor of 1.0, most closely predicted the measured performance of the existing drains under all conditions. The accuracy of the equations, and the range in average absolute deviation in drain spacing predictions (in brackets), was Bouwer and van Schilfgaarde, C=1.0 (4 to 9%) > van Schilfgaarde (6 to 13%) > Modified Glover (10 to 16%) > Bouwer and van Schilfgaarde, C=0.8 (11 to 19%) > Glover for drains placed on the barrier (23 to 40%) > Hammad, thick layers (40 to 59%) > Hammad, thin layers (35 to 110%). Individual equations generally predicted according to theory, provided the theoretical assumptions of the equations approximated field conditions.